It is the turn-off (recovery) time that is much longer however but this lazy diode is often used in \$RCD\$ clamps of cheap adapters below 30 W because it nicely damps the oscillations at turn-off and reduces radiated EMI.Īlso, surprisingly, the peak current going into the \$RCD\$ is often less than the power switch peak at the opening event. People usually believe that the diode should be ultra-fast but it is little known that the turn-on time of a 1N4007 nicely competes with that of a MUR160 for instance. The capacitor value is more in the vicinity of 1 to 47 nF perhaps, as a very rough figure while the resistance cannot be too low considering the dissipated power. Depending on the drive scheme, the MOSFET size, the input voltage and the primary inductance, there can be some significant overshoots destroying the MOSFET quite quickly. That duration is the time needed by the controller to effectively turn the MOSFET off when the current sense pin has detected a maximum. Now, I have simulated my circuit and tweaking values on C and R I came out with C=680uF and R=2.2kOhm the problem is they are simulated values and I've really not applied any formula. I already know the diode to use I just need to design the R and C value. ![]() I have a DC/DC flyback converter and I need to design a snubber.
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